Recording medium, recording apparatus and recording method

ABSTRACT

A recording medium of the recordable type in the form of a multi-layer disc or the like which is improved in compatibility and feasibility in use and a recording apparatus and a recording method ready for the recording medium are disclosed. A region for recording interlayer folding back position information is set on the recording medium (for example, “End sector number in Layer 0” or a session item type 3). In response to a fact that recording on a certain recording layer reaches a maximum recording range or that data recording advances from a certain recording layer to a next recording layer, interlayer folding back position information is recorded on the recording medium. This signifies that such recording is performed when advancement of the data recording to another recording layer is performed at a stage prior to disc closing or session closing or when it is predicted that such advancement of the data recording occurs soon. Also where the disc is of the type for which multi-session recording is performed, interlayer folding back position information is recorded with regard to a session in which folding back is performed.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a recording medium which includes aplurality of information recording layers and a recording apparatus anda recording method ready for a recording medium of the type mentioned.

[0002] Optical discs, optical cards and so forth are known as opticalrecording media on or from which information can be recorded orreproduced optically. A laser beam of a semiconductor laser or a likeelement is used as a light source and converged by a lens to form alight spot which is illuminated upon an optical recording medium of thetype mentioned to record or reproduce information on or from the opticalrecording medium.

[0003] Development of a technique for further increasing the recordingcapacity of such optical recording media as described above has been andis being carried out energetically. Conventional effects to increase theinformation recording density on an optical disc have been directedprincipally to increase of the recording density on a recording surfaceof the disc. For example, it has been attempted to reduce the trackpitch and/or raise the recording density in a linear velocity directionin recording and reading scanning, for example, in combination with adecrease in wavelength of a light source for emitting a recording beamor with signal processing of a reproduction system.

[0004] However, even if the wavelength of the light source is reduced,it is limited down to the ultraviolet region. Meanwhile, the pit sizecan be reduced to a level with which the pit can be transferred to adisc upon cutting. Therefore, as far as a two-dimensional region of adisc is utilized, the attempts to raise the recording density arelimited soon.

[0005] Therefore, also a technique which makes use of athree-dimensional region is attempted to increase the capacity of adisc. In particular, attention is paid to a multi-layer disc wherein aplurality of information recording layers are layered in order tofurther increase the recording information density in the thicknesswisedirection of a disc.

[0006] A multi-layer recording medium in which a plurality of recordinglayers are layered is characterized in that it can have a recordingcapacity increased in accordance with the number of recording layers andcan be combined readily with other high density recording techniques. Asone of such multi-layer recording discs, for example, a DVD-ROM (DigitalVersatile Disc ROM) which is a reproduction-only optical disc has beenplaced into practical use.

[0007] Several documents such as U.S. Pat. No. 5,740,136, No. 5754507,No. 5682372, No. 5920527, No. 6061310, No. 6330212 and No. 6552971disclose techniques applied to a DVD-ROM or the like which includes tworecording layers.

[0008] It is expected that not only multi-layer media of the ROM typebut also recordable multi-layer recording media wherein a plurality ofrecording layers of a phase change material, a magneto-optical materialor a dye material are layered can be placed into practical use infuture. For example, as regards discs of the DVD type, it is estimatedthat multi-layer recording layers are implemented also with discs of thewrite-once type called DVD−R or DVD+R and discs of the rewritable typecalled DVD−RW or DVD+RW.

[0009] Incidentally, where a recording operation is performed for amulti-layer recording medium, movement of the recording point betweenlayers is performed in the recording process. For example, the recordinglayers of a two-layer disc are possibly used in such a form that datarecording is performed first for the first layer (layer 0) and then datarecording is performed for the second layer (layer 1).

[0010] Where the multi-layer recording medium is a reproduction-onlydisc such as a DVD-ROM described above, since the amount of datarecorded on the disc in advance is known and no user data are written onthe disc any more, the folding back position of the reading point inmovement between layers is fixed, and the folding back position may berecorded, for example, in management information in the lead-in area.More particularly, information of the last end position of the layer 0may be recorded.

[0011] However, where discs which allow recording such as write-oncetype discs or rewritable type discs are considered, only if informationof a fixed folding back position is recorded merely in the lead-in areaor the like, this is insufficient for practical use.

[0012] For example, in a recordable disc, information of the lead-inarea and so forth is not finally determined until after the entire discis closed (or finalized) after data recording. In this instance, thefolding back position information is not recorded until after discclosing is performed.

[0013] Further, when additional writing is performed in a multi-sessionsystem, since information of the lead-in area is written upon closing ofthe first session, actual folding back position information is notreflected. For example, if recording of the second session is performedafter the first session is closed and the second session extends fromthe layer 0 to the layer 1, the actual folding back position informationis not recorded as information of the lead-in area.

[0014] The situations described above give rise to a problem that such asituation that a disc recording and reproduction apparatus cannotactually grasp the folding back position accurately occurs and thisdeteriorates the compatibility and the feasibility in use of the disc.

SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide a recordingmedium of the recordable type having a plurality of recording layerswhich allows folding back position information to be managed accuratelyto assure the compatibility and the feasibility in use of the disc and arecording apparatus and a recording method which are ready by whichfolding back position information of a recording medium of the typedescribed can be managed accurately.

[0016] In order to attain the object described above, according to anaspect of the present invention, there is provided a recording medium,including a plurality of recording layers into which data can bewritten, each of the recording layers having formed thereon a data areainto and from which main data are to be recorded and reproduced, apreceding area formed at a position preceding to the data area, and anend area succeeding the data area, the recording medium having a regioninto which, in response to a fact that recording on a certain one of therecording layers reaches a maximum recording range or that datarecording advances from a certain one of the recording layers to a nextone of the recording layers, interlayer folding back positioninformation indicative of a position to which the data recordingadvances is to be recorded.

[0017] According to another aspect of the present invention, there isprovided a recording apparatus for a recording medium which has aplurality of recording layers into which data can be written and each ofwhich has a data area into and from which main data are to be recordedand reproduced, a preceding area formed at a position preceding to thedata area, and an end area succeeding the data area, including arecording block for recording information on any of the recordinglayers, and a control block for controlling, when, in a recordingoperation by the recording block, recording on a certain one of therecording layers reaches a maximum recording range or data recordingadvances from a certain one of the recording layers to a next one of therecording layers, the recording block to record interlayer folding backposition information indicative of a position to which the datarecording advances into a predetermined region on the recording medium.

[0018] According to a further aspect of the present invention, there isprovided a recording method for recording on a recording medium whichhas a plurality of recording layers into which data can be written andeach of which has a data area into and from which main data are to berecorded and reproduced, a preceding area formed at a position precedingto the data area, and an end area succeeding the data area, including astep of recording information on any of the recording layers, and a stepof controlling, in response to a fact that recording on a certain one ofthe recording layers reaches a maximum recording range or data recordingadvances from a certain one of the recording layers to a next one of therecording layers at the recording step, so that interlayer folding backposition information indicative of a position to which the datarecording advances is recorded into a predetermined region on therecording medium.

[0019] In the recording medium, recording apparatus and recordingmethod, interlayer folding back position information is recorded intothe predetermined region on the recording medium in response to a factthat recording on a certain one of the recording layers reaches amaximum recording range or that data recording advances from a certainone of the recording layers to a next one of the recording layers. Thissignifies that interlayer folding back position information is recordedwhen advancement of the data recording to another recording layer isperformed at a stage before disc closing or session closing is performedor when it is predicted that such advancement of the data recordingoccurs soon. Accordingly, the recording apparatus or a reproductionapparatus can grasp the interlayer folding back position information ofthe disc even if the disc is in a stage before disc closing or sessionclosing is performed for the disc.

[0020] Further, where the disc is of the type for which multi-sessionrecording is performed, when interlayer folding back occurs or when asession is closed, correct interlayer folding back position informationin the session is recorded on the disc. Also in this instance, therecording apparatus or a reproduction apparatus can grasp the correctinterlayer folding back position information of the disc.

[0021] Accordingly, the recording apparatus and the reproductionapparatus can correctly grasp the interlayer folding back positioninformation of the disc even if the disc at a stage before disc closingor session closing is performed for the disc or the disc is of the typefor which multi-session recording is performed. Consequently, there isan advantage that the compatibility and the feasibility in use of arecording and/or reproduction system in which a recording medium is usedcan be improved.

[0022] More particularly, even if the disc recorded by a certainrecording apparatus is not closed, it can be recorded using anotherrecording apparatus as well. Further, even if the disc recorded by acertain recording apparatus is of the multi-session type, it can berecorded or reproduced well using another recording apparatus or anotherreproduction apparatus as well. Also the feasibility in use of the useris improved thereby.

[0023] Where the region into which the interlayer folding back positioninformation is to be recoded is provided in the data area, particularly,for example, in a region of an intro or a closure which are provided asfront and rear ends of a session in the data area, the interlayerfolding back position information can be recorded and confirmed readilyin a unit of a session. Further, in a session whose portioncorresponding to the intro is a preceding area, the interlayer foldingback position information may be recorded in the preceding area whichmay be, for example, a lead-in area or a middle area, but in anothersession whose portion corresponding to the closure is an end area, theinterlayer folding back position information may be recorded in the endarea which may be, for example, a lead-out area or a middle area.

[0024] Further, if advancement of the data recording from a certain oneof the recording layers to a next one of the recording layers isperformed within a certain session, then it is appropriate to record theinterlayer folding back position information when the session is closed,and this makes it possible to accurately record the interlayer foldingback position information on the disc particularly of the multi-sessiontype.

[0025] Furthermore, when the recording medium is to be unloaded, ifadvancement of the data recording from a certain one of the recordinglayers to a next one of the recording layers is performed within asession on the recording medium which is not closed as yet and recordingof the interlayer folding back position information is executed,recording of the interlayer folding back position information can beimplemented appropriately with the disc before it is closed.

[0026] This similarly applies also where recording of the interlayerfolding back position information is performed in response to aninstruction from a host apparatus.

[0027] Further, if the interlayer folding back position information isrecorded when advancement of the data recording by a recording operationfrom a certain one of the recording layers to a next one of therecording layers is performed, then when an event of interlayer foldingback occurs, the interlayer folding back position information in thisinstance is assured immediately on the recording medium. Therefore, evenif, for example, interruption of power supply or the like occurs later,the correct interlayer folding back position information can beobtained.

[0028] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionand the appended claims, taken in conjunction with the accompanyingdrawings in which like parts or elements denoted by like referencesymbols.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a diagrammatic view illustrating an area structure andPSN of a disc;

[0030]FIG. 2 is a view illustrating an information zone of amulti-session disc;

[0031]FIG. 3 is a view illustrating a disc control block;

[0032]FIG. 4 is a schematic view showing a two-layer disc;

[0033]FIGS. 5A and 5B are diagrammatic views illustrating a paralleltrack path;

[0034]FIGS. 6A and 6B are diagrammatic views illustrating an oppositetrack path;

[0035]FIG. 7 is a view illustrating physical format information;

[0036]FIG. 8 is a view illustrating a data area allocation field;

[0037]FIGS. 9A and 9B are views illustrating recorded states on anopposite track path;

[0038]FIG. 10 is a view illustrating a multi-session recorded state onan opposite track path;

[0039]FIG. 11 is a view illustrating an SDCB of a disc of to which thepresent invention is applied;

[0040]FIGS. 12A to 12C are views illustrating session items on the discillustrated in FIG. 11;

[0041]FIGS. 13A to 13C are views illustrating fragment recording andSDCB updating within a session;

[0042]FIG. 14 is a block diagram showing a recording and reproductionapparatus to which the present invention is applied;

[0043]FIG. 15 is a flow chart illustrating a session closing process ofthe recording and reproduction apparatus of FIG. 14;

[0044]FIG. 16 is a flow chart illustrating an SDCB updating process uponejection of the recording and reproduction apparatus of FIG. 14;

[0045]FIG. 17 is a flow chart illustrating an SDCB updating process uponoccurrence of an interlayer folding back of the recording andreproduction apparatus of FIG. 14; and

[0046]FIG. 18 is a diagrammatic view illustrating an SDCB updatingprocess upon occurrence of an interlayer folding back of the recordingand reproduction apparatus of FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0047] In the following, a preferred embodiment of the present inventionis described in the following procedure.

[0048] 1. Disc

[0049] 1-1. Area Structure of a Recording Layer

[0050] 1-2. Two-Layer Disc

[0051] 1-3. Example I of Recording of Interlayer Folding Back PositionInformation

[0052] 1-4. Example II of Recording of Interlayer Folding Back PositionInformation

[0053] 2. Disc Drive Apparatus

[0054] 2-1. Apparatus Configuration

[0055] 2-2. Session Closing Process

[0056] 2-3. Processing upon Ejection

[0057] 2-4. SDCB Updating Process upon Occurrence of Interlayer FoldingBack

[0058] 3. Modifications

[0059] 1. Disc

[0060] 1-1. Area Structure of a Recording Layer

[0061] In a preferred embodiment of the present invention, a DVD(Digital Versatile Disc) is taken as an example of a large capacity discrecording medium, and a disc drive apparatus hereinafter describedperforms recording and reproduction of a disc in the form of a DVD.

[0062] A plurality of standards such as DVD+R, DVD−R, DVD−RW and DVD−RAMare available for discs of the DVD type which allow recording. In thefollowing description of the present specification, a DVD+R which is awrite-once medium is taken as an example.

[0063] If a disc in the form of a DVD+R is loaded into a disc driveapparatus (recording apparatus), then information unique to the disc isread out from ADIP (Address in pre-groove) information engraved on awobbling groove on a recording surface of the disc, and it is recognizedthat the disc loaded is a DVD+R disc. The recognized disc is recordedand then unloaded from the recording apparatus soon, and may thereafterbe loaded again. In this instance, the disc may be loaded into the samerecording apparatus again or may otherwise be loaded into some otherrecording apparatus or reproduction apparatus for data exchange.

[0064] Taking such forms of use into consideration, a logical format ofthe DVD is prescribed in order to make smooth recording exchange andreproduction exchange between apparatus.

[0065]FIG. 1 shows a layout of a recording layer of the DVD+R.

[0066] Referring to FIG. 1, in a logical data layout in the recordinglayer of the DVD+R, an information zone is formed from the innercircumference side to the outer circumference side of the disc. Theinformation zone is a region which includes all necessary information tosecure recording exchange and reproduction exchange of data.

[0067] The information zone includes one or a plurality of sessions.

[0068] The information zone is principally composed of the followingfive areas.

[0069] [1] Inner drive area

[0070] [2] Lead-in zone (also called lead-in area)

[0071] [3] Data zone (also called data area)

[0072] [4] Lead-out zone (also called lead-out area)

[0073] [5] Outer drive area

[0074] The lead-in zone, data zone and lead-out zone are regions whichcan be accessed without any trouble also by an apparatus for exclusiveuse for reproduction.

[0075] The inner drive area and the outer drive area are regions forexclusive use for a recording apparatus. When information is to berecorded, the laser power upon recording must be adjusted so thatcorrect recording marks can be formed. To this end, a test zone whichcan be used for test recording for determining optimum recordingconditions and a region into which management information regardingrecording conditions can be recorded are formed in the inner drive areaand the outer drive area. Since the recorded state of the test zone isrendered ununiform by test recording, there is no guarantee that thetest zone can be accessed without any trouble by an apparatus forexclusive use for reproduction, and therefore, the test zone is disposedat a position at which it cannot be accessed by an apparatus forexclusive use for reproduction.

[0076] A physical sector number (PSN) is applied as information of anabsolute position on the disc.

[0077] As seen in FIG. 1, the value of the physical sector numberincreases, for example, from the inner circumference side to the outercircumference side of the disc. In the DVD+R, PSN=2FFFFh (any value withh added thereto is represented in hexadecimal notation) is determined asthe last end of the lead-in zone, and the data zone starts fromPSN=30000h.

[0078] The data zone basically is a region into which user data arewritten whereas management information is written in the lead-in zone.On the other hand, the lead-out zone is subject to writing of dummy datain order to maintain the compatibility with, for example, areproduction-only disc, but sometimes undergoes writing of managementinformation.

[0079] In order to maintain the compatibility with a reproduction-onlydisc, it is necessary to complete recording with a session configurationwhich includes the lead-in zone, the data zone in which an unrecordedportion does not remain, and the lead-out zone.

[0080] In the case of a write-once medium, after user data are writteninto the data zone, when the session (or the entire disc) is to beclosed, an appropriate management method is recorded into the lead-inzone to make it possible for the medium to be reproduced also by anotherreproduction apparatus as known in the art. In other words, when thedisc is not in a closed state, that is, when the disc is in an openstate, since appropriate management information is not written in thelead-in zone as yet, the disc does not have the reproductioncompatibility at the point of time.

[0081] Namely, the reproduction compatibility is obtained by performinga closing process for the disc at a point of time before writing on thedisc is not performed newly after necessary writing is completed. Afterthe reproduction compatibility is obtained, the disc does not allow anyfurther writing thereon. On the other hand, when the disc is in an openstate, although it does not have the reproduction compatibility as yet,it allows further data writing.

[0082] To complete recording with a session configuration which includesthe lead-in zone, the data zone in which an unrecorded portion does notremain, and the lead-out zone described above signifies to perform aclosing process.

[0083] Such a situation as just described gives rise to a problem uniqueto a write-once disc that, once recording is completed with a sessionconfiguration on a disc as a DVD+R, even if the remaining part of thedisc is in a non-recorded state, the non-recorded part cannot beutilized any more.

[0084] Therefore, a concept of multi-sessions which secure thereproduction compatibility only by modifying an apparatus for exclusiveuse for reproduction in the minimum has been introduced to moderate theproblem of the single session layout that the remaining non-recordedpart is wasted.

[0085] In the case of a DVD+R, a multi-session disc allows presence of aplurality of sessions up to the 191st session.

[0086] Each of the sessions includes

[0087] [1] an intro,

[0088] [2] a data zone, and

[0089] [3] a closure.

[0090] One session is enabled for data recording by opening (an openingprocess) and completed by closing (a closing process).

[0091] If a non-recorded data zone remains on the disc, then a sessioncan be added by the opening. At this time, data of an inner side sessioncan be imported logically to the new session. The intro and the closureplay rolls similar to those of the lead-in zone and the lead-out zonedescribed hereinabove, respectively. The two regions temporarily storecurrent information while the lead-in zone or information of the lead-inzone is updated, and, since they record the information as ordinary dataas an attribute thereof, they have the different names from each otherapplied thereto.

[0092]FIG. 2 shows a multi-session layout.

[0093] Referring to FIG. 2, in the information zone, a session 1, asession 2, . . . , and a session N are formed in order from the top inthe region from the lead-in zone to the lead-out zone.

[0094] The first session 1 includes the lead-in zone, a data zone and aclosure.

[0095] The session 2 includes an intro, a data zone and a closure

[0096] The last session N includes an intro, a data zone and thelead-out zone.

[0097] As can be recognized from the comparison with FIG. 1, in themulti-session disc, the top session 1 includes the lead-in zonepreceding to the data zone of FIG. 1.

[0098] Meanwhile, the last session N includes the lead-out zonefollowing the data zone of FIG. 1.

[0099] Further, while it is necessary for one session to complete with alead-in zone, a data zone and a lead-out zone as described hereinabove,in the case of a multi-session disc, all of the sessions cannot includea lead-in zone and a lead-out zone, and therefore, regions for an introand a closure are formed in each session.

[0100] For example, in the session 1, a closure is formed in place of alead-out zone. In the session 2, an intro and a closure are formed inplace of a lead-in zone and a lead-out zone, respectively. In the lastsession N, an intro is provided in place of a lead-in zone.

[0101] Then, the data zone appearing in FIG. 1 is composed of the datazones from the data zone of the session 1 to the data zone of thesession N shown in FIG. 2. Thus, the intros and the closures areincluded in the data zone appearing in FIG. 1, and this is the reasonwhy the intro and the closure are recorded as ordinary data as anattribute thereof as described hereinabove.

[0102] As seen in FIG. 2, the lead-in zone includes an inner discidentification zone.

[0103] Meanwhile, the lead-out zone includes an outer discidentification zone.

[0104] The intro includes an inner session identification zone.

[0105] The closure includes an outer session identification zone.

[0106] The zones mentioned are hereinafter referred to collectively asidentification zones. In each of the identification zones, informationcalled disc control block (DCB) is recorded.

[0107] The disc control block (DCB) is prepared in order to allowaddition of recording compatibility information to the configuration onthe disc.

[0108] The disc control block (DCB) has a general format illustrated inFIG. 3 and includes 16 physical sectors from sector 0 to sector 15. Onephysical sector is composed of 2,048 bytes.

[0109] The first 40 bytes (byte positions D0 to D39) of all of the disccontrol blocks (DCB) have the same format.

[0110] As seen in FIG. 3, the disc control blocks (DCB) include suchinformation as a content descriptor and a drive ID.

[0111] Each identification zone allows recording of 16 DCBs in themaximum.

[0112] In the DVD+R, a special session DCB (SDCB) is defined as a DCB tobe recorded in the outer session identification zone and the innersession identification zone. The SDCB is defined in order to reflectstates of a plurality of sessions. The structure of the SDCB of the discof the present embodiment is hereinafter described with reference toFIG. 11.

[0113] The lead-in or the intro of an open session has an SDCB whichdescribes the configuration of the open session and all of the precedingsession positions. Then, when the session is closed, the SDCB in theinner identification zone is updated, and one copy of it is recordedinto the outer identification zone.

[0114] 1-2. Two-Layer Disc

[0115] Here, as a DVD of a recordable type, a two-layer DVD having tworecording layers is considered. The two-layer DVD has a structurewherein two recording layers each in the form of a dye change recordingfilm or a phase change recording film are layered with a comparativelysmall gap left therebetween.

[0116]FIG. 4 schematically shows a disc 1 in a state wherein a layer 0and another layer 1 are layered as the two recording layers.

[0117] Upon recording of such a two-layer disc as just described, alaser beam emitted from an optical pickup 3 of a disc drive apparatusthrough an objective lens 3 a is focused on one of the two recordinglayers to record a signal on the recording layer.

[0118] For a two-layer disc, two recording methods called parallel trackpath and opposite track path are available.

[0119]FIGS. 5A and 5B illustrate the parallel track path recordingmethod.

[0120] It is to be noted that, as described hereinabove, the physicalsector number PSN is an actual address recorded on a disc surface. Incontrast, the logical block address LBA is an address applied to a listof logical data handled by a computer. The PSN and the LBA correspondone by one to each other.

[0121] In the parallel track path illustrated in FIG. 5A, each of thelayers 0 and 1 includes a lead-in area, a data area and a lead-out areaformed from the inner circumference side to the outer circumferenceside.

[0122] Recording of data begins with Start PSN (=30000h) on the innercircumference of the layer 0 and ends with End PSN (0) which is the lastend of the data area of the layer 0. Thereafter, recording is performedin order beginning with Start PSN (=30000h) on the inner circumferenceside of the layer 1 and ending with End PSN (1) on the outercircumference side.

[0123] The physical block address LBA is allocated successively in orderin the direction from the inner circumference side to the outercircumference side of the layer 0 and then from the inner circumferenceside to the outer circumference side of the layer 1 as seen in FIG. 5B.

[0124] The opposite track path is illustrated in FIGS. 6A and 6B. On adisc to be recorded by the opposite track path recording method,recording is performed in order such that it is recorded toward the lastend of the layer 0 beginning with the inner circumference of the layer 0and is then recorded toward the inner circumference of the layer 1beginning with the outer circumference of the layer 1.

[0125] As seen in FIG. 6A, in the opposite track path, a lead-in area, adata area and a middle area are formed in order from the innercircumference side to the outer circumference side on the layer 0.Further, another middle area, another data area and a lead-out area areformed from the outer circumference side to the inner circumference sideon the layer 1.

[0126] Recording of data begins with Start PSN (=30000h) on the innercircumference of the layer 0 and is performed up to End PSN (0) which isthe last end of the data area of the layer 0. Thereafter, recording ofdata is performed beginning with the outer circumference side (invertedEnd PSN (0)) and ending with End PSN (1) on the inner circumference sideof the layer 1.

[0127] The logical block address LBA is applied successively in order inthe direction wherein it is applied successively from the innercircumference side to the outer circumference side of the layer 0 andthen applied in a folding back manner from the outer circumference sideto the inner circumference side of the layer 1.

[0128] In this manner, the parallel track path and the opposite trackpath are different from each other in the physical storage method(order) of data.

[0129] Further, in the opposite track path, a middle area isadditionally provided on the outer circumference side with respect tothe interlayer folding back portion. This arises from the followingreason. In the opposite track path, the lead-in area is formed on thelayer 0, and the lead-out area is formed on the layer 1. Therefore, nolead-in area/lead-out area is formed on the outer circumference sidewith respect to the data area. On the other hand, since an apparatus forexclusive use for reproduction reads pits recorded on the disc surface,in a region which includes no pit, the apparatus cannot read out datastably because no servo control is applied. Therefore, a region for theguard is required. From this requirement, a middle area is formed on theouter circumference side and has, for example, dummy data recordedtherein so that a function similar to that of the lead-out area isprovided to the middle area.

1-3. Example 1 of Recording of Interlayer Folding Back PositionInformation

[0130] In the discs shown in FIGS. 5A, 5B and 6A, 6B, it is assumed thatthe data zone (data area) is used fully for recording in a singlesession configuration.

[0131] Here, a two-layer disc as a reproduction-only disc (DVD-ROM,DVD-Video or the like) is described. A reproduction-only disc allowsdiscrimination of an interlayer folding back position from informationin the lead-in area (including contents same as those in the lead-in ofFIG. 2).

[0132] The lead-in area of the DVD system is structured such that, ascan be seen from reference to the lead-in area of FIG. 2, a control datazone is provided and has such physical format information as illustratedin FIG. 7 recorded therein.

[0133] Referring to FIG. 7, the physical format information is recordedin a region of 2,048 bytes (one sector), and contents of each byte aredefined. In particular, such information as a book type and partversion, a disc size, a minimum read-out rate, a disc structure, arecording density, a data area allocation and a BCA descriptor isrecorded.

[0134] In the physical format information, the data area allocation atthe byte positions 4 to 15 is defined in such a manner as illustrated inFIG. 8. It is to be noted that FIG. 8 illustrates the data areaallocation with regard to a single layer disc, a two-layer disc of theparallel track path and a two-layer disc of the opposite track path.

[0135] In the field of the data area allocation, the start sector numberof the data area is recorded at the byte positions 5 to 7. At the bytepositions 9 to 11, the end sector number of the data area is recorded.They are common to all of the single layer disc, parallel track pathdisc and opposite track path disc.

[0136] At the byte positions 13 to 15, no effective information isrecorded on the single layer disc and the parallel track path disc, butthe last sector number of the layer 0 is recorded on the opposite trackpath disc. The last sector number is interlayer folding back positioninformation. A disc drive apparatus grasps the last end position of datain the layer 0 from the information and discriminates that continueddata are recorded on the layer 1.

[0137] In summary, the reproduction-only single layer disc naturallyrequires no interlayer folding back position information.

[0138] The reproduction-only parallel track path disc has a lead-in areaprovided on each of the recording layers. The end position of eachrecording layer can be discriminated by confirming the end sector numberof the data area at the byte positions 9 to 11 described hereinabovewith reference to FIG. 8 in the lead-in area. Accordingly, since thelast end of data in each recording layer can be discriminated, theinformation of the byte positions 13 to 15 is not required.

[0139] In the reproduction-only opposite track path disc, the lead-inarea is provided only on the layer 0. Then, the end sector number of thedata area at the byte positions 9 to 11 of FIG. 8 represents the addressimmediately preceding to the lead-out, for example, in the layer 1.Therefore, the interlayer folding back position cannot be discriminatedfrom this information. Therefore, the interlayer folding back positioninformation at the byte positions 13 to 15 is recorded.

[0140] A disc drive apparatus can grasp the interlayer folding backposition of a two-layer disc as a reproduction-only disc from suchinformation in the lead-in area as described above. Information of thelead-in area of such a structure as described above is adopted also byrecordable discs such as a DVD+R disc.

[0141] However, where a disc which is of the recordable type such as aDVD+R disc and besides has a plurality of recording layers such as twolayers has only such information as described above, it is practicallyinconvenient.

[0142] In particular, in a DVD+R disc or the like, the lead-in area isrecorded by a disc closing process performed for a single session discor by a session closing process of the first session for a multi-sessiondisc.

[0143] This is because, with a disc of the recordable type, it is notknown in advance what amount of data will be recorded on the disc in thefuture, and while recording is performed successively, the state of thedisc varies every moment. The disc state or the session state is notdetermined until after a closing process is performed.

[0144] Thus, in an open state before the closing process is performed,such information as illustrated in FIG. 8 is not present as effectiveinformation in the lead-in area. In other words, even if recording isperformed already across layers, as far as the layers remain in an openstate, the interlayer folding back position cannot be discriminated.

[0145] For example, if it is assumed that a disc which remains in anopen state is unloaded from a recording apparatus and loaded intoanother recording apparatus, then the second recording apparatus cannotgrasp the interlayer folding back position and cannot operate normally.

[0146] Where the disc is recorded by multi-session recording and allowswriting, information in the lead-in area is determined upon a closingprocess for the first session. Therefore, even if data recording isperformed across recording layers in a succeeding session, theinformation in the lead-in area does not reflect the actual interlayerfolding back position. Also in this instance, the disc drive apparatusis placed into a situation in which it cannot discriminate theinterlayer folding back position.

[0147] Those are described with reference to FIGS. 9A, 9B and 10.

[0148]FIGS. 9A and 9B show a disc of the opposite track path as anexample.

[0149] Referring to FIGS. 9A and 9b, reference character “UA” representsa region (Unrecorded Area) in which no pit is present, referencecharacters “DA1” to “DA12” denote recorded user data, referencecharacter “LI0” denotes the lead-in of the layer 0, “LO1” the lead-outof the layer 1, “MA0” the middle area of the layer 0, and the “MA1” themiddle area of the layer 1.

[0150]FIG. 9A illustrates a state wherein the user data DA1 to DA12 arerecorded sequentially by single session recording. It is assumed that,for example, the user data DA1 to DA10 are recorded on the layer 0, andthe user data DA11 to DA12 are recorded on the layer 1.

[0151] This state still is a recordable state (open state), and thelead-in area and the lead-out area are not added.

[0152] Accordingly, the physical format information describedhereinabove with reference to FIGS. 7 and 8 does not exist, andtherefore, the interlayer folding back position of data is unknown.

[0153]FIG. 9b shows a disc layout when the sessions are closed later. Bythe session closing, also the data area recorded on the surface of thedisc is determined, and the lead-in area and the lead-out area areadded. It is to be noted that the region of the data area of the layer 1in which no user data has been recorded is filled with lead-out data(dummy data).

[0154] After the state of FIG. 9B is reached, contents of the physicalformat information described hereinabove with reference to FIGS. 7 and 8can be referred to and also the interlayer folding back position of datacan be known.

[0155] After all, if session closing is performed taking reproductioncompatibility into consideration, then although the interlayer foldingback position can be grasped, the remaining unrecorded part cannot beutilized any more. On the other hand, even if it is tried to assurerecording compatibility between apparatus while the disc remains in anopen state, recording compatibility cannot be assured inconvenientlybecause the interlayer folding back position is unknown.

[0156] While FIGS. 9A and 9B show a two-layer disc of the opposite trackpath as an example, the description above similarly applies also to atwo-layer disc of the parallel track path.

[0157] From the foregoing, also in order to assure recordingcompatibility, it is necessary for the interlayer folding back positionto be stored temporarily or permanently somewhere on a recording medium.

[0158] Different situations in the case of multi-session recording aredescribed with reference to FIG. 10. In FIG. 10, reference characters“UA”, “DA1” to “DA12”, “LI0”, “MA0” and “MA1” are similar to those ofFIGS. 9A and 9B. Further in FIG. 10, reference character “CL1” denotesthe closure of the session 1, “CL2” the closure of the session 2, and“IT2” the intro of the session 2.

[0159]FIG. 10 illustrates that user data DA1 to DA6 are recorded as thesession 1, and user data DA7 to DA12 are recorded as the session 2. Itis assumed that interlayer folding back is performed in the session 2.

[0160] In this instance, although the sessions 1 and 2 are closed, a newsession or sessions can be added to the disc as a whole. Accordingly,the session 1 is formed from the lead-in area LI0, user data DA1 to DA6and closure CL1. Meanwhile, the session 2 is formed from the intro IT2,user data DA7 to DA12 and closure CL2.

[0161] In this instance, since the lead-in area LI0 is added, thephysical format information described hereinabove with reference toFIGS. 7 and 8 exists. However, since information of the entire disc isrecorded in the physical format information and is written before thesession 2 is recorded, useful information of the interlayer folding backposition which accurately reflects the interlayer folding havingappeared in the session 2 is not recorded.

[0162] According to a disc recognition method of a reproductionapparatus, the lead-in area LI0 is read first to recognize the session1. Thereafter, the intro IT2 of the session 2 is read in to recognizethe session 2. Such a process as just described is repeated to recognizethe disc. However, since effective interlayer folding back positioninformation is not recorded in the lead-in area LI0, the interlayerfolding back position of the session 2 cannot be grasped.

[0163] Taking this into consideration, if the interlayer folding backposition information is added to the intro IT2 when the session 2 isclosed, then the interlayer folding back position information can beacquired smoothly and conveniently.

[0164] Further, it is recognized that it is preferable to have theinterlayer folding back position information recorded on the disc beforesession closing is performed and particularly when a session at whichinterlayer folding back has occurred on a multi-session disc is closedor the like principally from the two situations described hereinabovewith reference to FIGS. 9A, 9B and 10.

[0165] It is to be noted that, while a disadvantage arising from thefact that, in the multi-session recording, even if a session is closed(even if the lead-in area of the first session exists), effectiveinterlayer folding back position information does not exist is describedwith reference to FIG. 10, a disadvantage similar to that describedabove with reference to FIGS. 9A and 9B may possibly occur also with themulti-session recording. This is because, for example, even ifinterlayer folding back is performed in a certain session, if thesession remains in an open state, then effective information indicativeof the interlayer folding back position does not exist.

[0166] In the present embodiment, a region in which the interlayerfolding back position information can be recorded is prepared in theSDCB described hereinabove.

[0167] As described hereinabove with reference to FIG. 2, anidentification zone is provided in each of the lead-in area, intro,closure and lead-out area, and a disc control block (DCB) is prepared inthe identification zone.

[0168] Here, it is described that, in the DVD+R, a session DCB (SDCB) isdefined in order to reflect a plurality of session states.

[0169] The format of the SDCB in the present embodiment is shown in FIG.11.

[0170] The SDCB extensively defines the DCB of FIG. 3 and accordingly isa region of 16 physical sectors.

[0171] As can be seen from comparison with the DCB of FIG. 3, the SDCBof FIG. 11 is similar up to the byte positions D0 to D39 of the physicalsector 0 to those of the DCB of FIG. 3.

[0172] In the SDCB, a session number is recorded at the byte positionD40.

[0173] Then, 4 bytes at the byte positions D42 to D45 form a region inwhich the end sector number in the layer 0 is recorded as the interlayerfolding back position information.

[0174] It is to be noted that the byte positions D42 to D45 form aregion which is defined as reserved (not defined) in the conventionalSDCB.

[0175] The disc ID is recorded at the byte positions D64 to D95, andpredetermined data are corded at the byte positions D96 to D127 inaccordance with an application.

[0176] At the byte positions D128 et seq., N session items are recorded.A session item is data of a unit of 16 bytes. The session item ishereinafter described.

[0177] In the present embodiment, a region in which the interlayerfolding back position information is to be recorded is prepared at thebyte positions D42 to D45 of the SDCB, and actual effective interlayerfolding back position information is recorded in this region in theintro or closure of a session in which the interlayer folding back isperformed. In any other session in which the interlayer folding back isnot performed, all zeros should be placed at the byte positions D42 toD45.

[0178] Since the SDCB is provided in the identification zone in thelead-in area, intro, closure and lead-out area, if the interlayerfolding back position information is recorded in the SDCB in a necessaryarea (the lead-in area, intro, closure or lead-out area) as occasiondemands, then the disadvantages described hereinabove with reference toFIGS. 9A, 9B and 10 can be eliminated.

[0179] Recording of the interlayer folding back position information inthe SDCB is hereinafter described as a process of a disc driveapparatus.

1-4. Example II of Recording of Interlayer Folding Back PositionInformation

[0180] Incidentally, it is considered possible to record the interlayerfolding back position information otherwise in the session item in theSDCB similarly. This example is described.

[0181] As described hereinabove with reference to FIG. 11, a region inwhich N session items of a unit of 16 bytes can be recorded is preparedin the SDCB.

[0182] In the present example, three types (type 1, type 2 and type 3)are defined for the session items as seen in FIG. 12A. The type 1 andthe type 2 are defined already, and the type 3 is information newlydefined for recording of the interlayer folding back positioninformation.

[0183] The type 1 of the session item is a fragment item. The fragmentis a recording unit in one session.

[0184] The fragment is described with reference to FIGS. 13A to 13C.

[0185]FIG. 13A illustrates a configuration of one session. Referring toFIG. 13A, one session is composed of a lead-in or intro, a data zone anda lead-out or closure as described hereinabove with reference to FIG. 2.The data zone is composed of a plurality of fragments Frag#1 to Frag#nas seen in FIG. 13A. Each of the fragments Frag#1 to Frag#n forms anadditional-writing unit in one session. For example, at a point of timebefore a session is closed, data writing is performed in a unit of afragment, and at a point of time when writing of one data is completed,that is, when one fragment is formed, an SDCB having the managementinformation for the fragment is written into the identification zone.

[0186] As described hereinabove, the identification zone which is aregion of 256 sectors allows recording of up to 16 SDCBs each formedfrom 16 sectors. This signifies that an SDCB can be written (updated) 16times. FIG. 13B illustrates a state wherein 16 SDCBs SDCB#1 to SDCB#16in the maximum are recorded in the identification zone. In a statewherein a plurality of SDCBs are recorded in the identification zone,the latest SDCB is regarded as effective information. For example, inthe state wherein 16 SDCBs SDCB#1 to SDCB#16 are recorded, the SDCBSDCB#16 is the latest SDCB.

[0187] Thus, since one SDCB is recorded (that is, the SDCB is updated)at a point of time when one fragment is recorded, 16 fragments in themaximum can be recorded for one session.

[0188] Since one SDCB is recorded at a point of time when one fragmentis formed, also at a point of time before the session is closed, it ispossible to manage information of fragments recorded already.

[0189] For example, referring to FIGS. 13B and 13C, at a point of timewhen the fragment Frag#1 is recorded first, the first SDCB#1 is recordedin response to the recording. The SDCB#1 includes management informationof the fragment Frag#1. Thereafter, when a next fragment Frag#2 isrecorded, the SDCB#2 is recorded. The SDCB#2 includes managementinformation of the fragments Frag#1 and Frag#2. The SDCB#1 is renderedineffective at this point of time.

[0190] However, the SDCB is written not only in a correspondingrelationship to a fragment, but one SDCB may be additionally recorded inresponse to some other situation. In FIGS. 13B and 13C, a situationthat, for example, an SDCB#3 is recorded from some situation beforerecording of the fragment Frag#3 is completed is indicated by a brokenline. In this instance, at a point of time when the fragment Frag#3 isrecorded, an SDCB#4 is recorded.

[0191] It is to be noted that, since one SDCB is recorded without failin response to formation of one fragment, where an SDCB is recorded fromsome reason other than completion of recording of a fragment Frag likethe SDCB#3, the number of fragments Frag which can be formed in thesession becomes smaller than 16.

[0192] The management information of the Fragment Frag in the SDCB formsthe session item of the type 1 described above.

[0193] Contents of the type 1 (fragment item) of the session item areillustrated in FIG. 12B.

[0194] Referring to FIG. 12B, in the session item of 16 bytes, threebytes at the byte positions 0 to 2 represent a fragment item descriptor.The fragment descriptor has a value indicating that the session item isan item of the “type 1”, that is, a fragment item.

[0195] A fragment number is recorded in 2 bytes at the byte positions 3and 4. In particular, the number (one of #1 to #16 in the maximum) of afragment Frag to which the fragment item corresponds is recorded.

[0196] A fragment start address is recorded in 3 bytes at the bytepositions 5 to 7. In particular, the start address of the fragment Fragto which the fragment item corresponds is recorded.

[0197] A fragment end address is recorded in 3 bytes at the bytepositions 8 to 10. In particular, the end address of the fragment Fragto which the fragment item corresponds is recorded.

[0198] Since an SDCB corresponding to one fragment includes such afragment item (session item type 1) as described above, information ofthe fragment can be managed.

[0199] For example, when the SDCB#1 of FIG. 13B is recorded after thefragment Frag#1 of FIG. 13C is recorded, the SDCB#1 includes onefragment item corresponding to the fragment Frag#1.

[0200] When the fragment Frag#2 is recorded and then the SDCB#2 isrecorded, the SDCB#2 includes two fragment items corresponding to thefragments Frag#1 and Frag#2, respectively.

[0201] The type 2 of the session item shown in FIG. 12A is a previoussession item. In particular, information of sessions preceding to thecurrent session is indicated. Although detailed description is omittedherein, for example, if the current session is the session #2, thenaddress information and so forth of the session #1 are indicated in theprevious session item, and if the current session is the session #5,then address information and so forth of the sessions #1 to #4 areindicated in the previous session item.

[0202] The session item type 3 is a layer item for recording interlayerfolding back position information therein. Contents of the session itemtype 3 are illustrated in FIG. 12C.

[0203] Referring to FIG. 12C, in the session item of 16 bytes, threebytes at the byte positions 0 to 2 represent a layer item descriptor.The layer item descriptor has a value indicating that the currentsession item is a “type 3” item, that is, a layer item.

[0204] A layer number is recorded in two bytes at the byte positions 3and 4.

[0205] A layer end address is recorded in 3 bytes at the byte positions8 to 10. The layer end address is an address of the last end of thelayer and thus represents interlayer folding back position information.

[0206] Also where a session item for recording interlayer folding backposition information is prepared as one of session items in this manner,interlayer folding back position information can be recorded in theSDCB.

[0207] Since the SDCB is provided in the identification zone in thelead-in area, intro, closure and lead-out area, if the interlayerfolding back position information is recorded in the SDCB in a necessaryarea (the lead-in area, intro, closure or lead-out area) as occasiondemands, then the disadvantages described hereinabove with reference toFIGS. 9A, 9B and 10 can be eliminated.

[0208] 2. Disc Drive Apparatus

[0209] 2-1. Apparatus Configuration

[0210] A disc drive apparatus of a preferred embodiment of the presentinvention which is ready for the disc 1 (such as a two-layer DVD+R) onwhich interlayer folding back position information is recorded in anSDCB as in the examples described above is described with reference toFIG. 14.

[0211]FIG. 14 is a block diagram showing part of a disc drive apparatusto which the present invention is applied.

[0212] The disc 1 is placed on a turntable not shown and is driven, uponrecording or reproduction operation, to rotate at a constant linearvelocity (CLV) or a constant angular velocity (CAV) by a spindle motor2. Then, data recorded in the form of embossed pits, dye change pits orphase change pits on the disc 1 are read out by an optical pickup 3.

[0213] Though not shown, the optical pickup 3 has various elementsincorporated therein including a laser diode serving as a laser beamsource, a plurality of photo-detectors for detecting reflected light,and an objective lens serving as an output end of the laser beam. Theoptical pickup 3 further includes an optical system for illuminating thelaser beam upon a recording surface of the disc 1 through the objectivelens and introducing the reflected light from the disc 1 to thephoto-detectors, and a two-axis mechanism for carrying the objectivelens thereon for movement in an tracking direction and a focusingdirection.

[0214] Meanwhile, the entire optical pickup 3 is mounted for movement ina radial direction of the disc 1 by a sliding drive section 4.

[0215] Reflected light information from the disc 1 is detected andconverted into electric signals corresponding to the received amounts oflight by the photo-detectors, and the electric signals are supplied toan RF amplifier 8.

[0216] The RF amplifier 8 includes a current to voltage conversioncircuit for converting output current from each of the photo-detectorsin the optical pickup 3 into a voltage, a matrix arithmeticoperation/amplification circuit and other necessary circuit elements andproduces necessary signals through a matrix arithmetic operationprocess. The RF amplifier 8 forms, for example, an RF signalrepresentative of reproduction data, and a focusing error signal FE anda tracking error signal TE for servo control.

[0217] The reproduction RF signal outputted from the RF amplifier 8 issupplied to a reproduction signal processing section 9 while thefocusing error signal FE and the tracking error signal TE are suppliedto a servo control section 10.

[0218] The reproduction RF signal obtained by the RF amplifier 8 issubject to binarization, PLL clock generation, a decoding process intoan EFM+ signal (8-16 modulation signal), an error correction process andso forth in the reproduction signal processing section 9.

[0219] The reproduction signal processing section 9 utilizes a DRAM 11to perform the decoding process and the error correction process. It isto be noted that the DRAM 11 is used also as a cache memory for storagedata acquired from a host interface 13 or for transferring data to ahost computer not shown.

[0220] The reproduction signal processing section 9 cumulatively storesdecoded data into the DRAM 11 serving as a cache memory.

[0221] As a reproduction output of the disc drive apparatus, the databuffered in the DRAM 11 are successively read out and outputted so as tobe transferred.

[0222] Further, the reproduction signal processing section 9 extracts,from within information obtained by the EFM+demodulation and the errorcorrection for the RF signal, subcode information, ATIP information, LPPinformation, ADIP information, sector ID information and so forth andsupplies the extracted information to a controller 12.

[0223] The controller 12 is formed from, for example, a microcomputerand controls the entire apparatus.

[0224] The host interface 13 is connected to an external host apparatussuch as a personal computer not shown and communicates reproductiondata, read/write commands and so forth with the host apparatus.

[0225] In particular, reproduction data stored in the DRAM 11 areoutputted and transferred to the host apparatus through the hostinterface 13.

[0226] On the other hand, read/write commands, recording data and othersignals are supplied from the host apparatus to the disc drive apparatusand buffered into the DRAM 11 or supplied to the controller 12 throughthe host interface 13.

[0227] When the write command and recording data are supplied from thehost apparatus, the disc drive apparatus performs recording on the disc1.

[0228] Upon recording of data, the recording data buffered in the DRAM11 are processed for recording by a modulation section 14. Inparticular, addition of error correction codes, EFM+modulation and soforth are performed for the recording data.

[0229] The recording data modulated in this manner are supplied to alaser modulation circuit 15. The laser modulation circuit 15 drives thesemiconductor laser in the optical pickup 3 in response to the recordingdata to output a laser beam in accordance with the recording datathereby to write the recording data on the disc 1.

[0230] Upon this recording operation, the controller 12 controls theoptical pickup 3 to illuminate the laser beam with a recording powerupon the recording region of the disc 1.

[0231] Where the disc 1 is of the write-once type wherein a dye changefilm is used as a recording layer, pits are formed by a dye change bythe illumination of the laser beam of the recording power.

[0232] On the other hand, where the disc 1 is of the rewritable typewherein a phase change film is used as a recording layer, the crystalstructure of the recording layer is changed by heating by the laser beamthereby to form phase change pits on the recording layer. In particular,various data are recorded as presence or absence of a pit anddifferences in length of such pits. Further, if a laser beam isilluminated again upon a portion of the recording layer at which a pitis formed, then the crystal state changed upon recording of data returnsto its original state by heating thereby to eliminate the pits and erasethe data.

[0233] The servo control section 10 produces various servo drive signalssuch as focusing, tracking, sliding and spindle servo drive signals fromthe focusing error signal FE and the tracking error signal TE from theRF amplifier 8, an spindle error signal SPE from the reproduction signalprocessing section 9 or the controller 12 and so forth so thatcorresponding servo operations may be executed.

[0234] In particular, the servo control section 10 produces a focusingdrive signal and a tracking drive signal in response to the focusingerror signal FE and the tracking error signal TE and supplies them to afocusing/tracking drive circuit 6. The focusing/tracking drive circuit 6drives a focusing coil and a tracking coil of the two-axis mechanism ofthe optical pickup 3. Consequently, a tracking servo loop and a focusingservo loop are formed from the optical pickup 3, RF amplifier 8, servocontrol section 10, focusing/tracking drive circuit 6 and two-axismechanism.

[0235] It is to be noted that, in order to render the focusing servooperative, a focus search operation must be executed first. The focussearch operation is an operation of compulsorily moving the objectivelens while the focusing servo is off to detect a position at which anS-shaped curve of the focusing error signal FE is obtained. As wellknown in the art, a linear region of an S-shaped curve of a focusingerror signal is a range within which the position of the objective lenscan be pulled in to a focused position by closing the focusing servoloop. Accordingly, while the objective lens is moved compulsorily as afocus search operation, the range within which the pull-in describedabove is possible is detected, and the focusing servo is renderedoperative at the point of time. As a result, a focusing servo operationby which the laser spot is kept in a focused state is achieved.

[0236] In the present example, the disc 1 may possibly have a two-layerstructure including the layer 0 and the layer 1 as describedhereinabove.

[0237] However, in order to perform recording or reproduction withrespect to the layer 0, the laser beam must be conditioned so as to befocused on the layer 0. On the other hand, in order to perform recordingor reproduction with respect to the layer 1, the laser beam must beconditioned so as to be focused on the layer 1.

[0238] A shift movement of the focus position between the layers 0 and 1is performed by a focus jumping operation.

[0239] The focus jumping operation is executed such that, while thelaser beam is in a focused state on one of the layers, the focusingservo is rendered inoperative and the objective lens is movedcompulsorily until it comes to a position within the focus pull-in rangeto the other layer (until an S-shaped curve is observed), and at thepoint of time, the focusing servo is rendered operative.

[0240] The servo control section 10 further supplies a spindle drivesignal produced in response to the spindle error signal SPE to a spindlemotor drive circuit 7. The spindle motor drive circuit 7 applies, forexample, a three-phase drive signal to the spindle motor 2 in responseto the spindle drive signal to rotate the spindle motor 2. The servocontrol section 10 generates the spindle drive signal further inresponse to a spindle kick/brake control signal from the controller 12so that the spindle motor drive circuit 7 executes also such operationsas starting, stopping, acceleration and deceleration of the spindlemotor 2.

[0241] The servo control section 10 further produces a slide drivesignal in response to the access execution control of the controller 12or a slide error signal obtained, for example, as a low frequency bandcomponent of the tracking error signal TE and supplies the slide drivesignal to a sliding drive circuit 5. The sliding drive circuit 5 drivesthe sliding drive section 4 in response to the slide drive signal.Though not shown, the sliding drive section 4 includes a mechanismincluding a main shaft for supporting the optical pickup 3, a threadmotor, a transmission gear mechanism and so forth, and when the slidingdrive circuit 5 drives the sliding drive section 4 in response to theslide drive signal, a required sliding movement of the optical pickup 3is performed.

[0242] 2-2. Session Closing Process

[0243] In the disc drive apparatus of the present embodiment, when suchinterlayer folding back as described above occurs, interlayer foldingback position information is recorded on the disc 1.

[0244] The recording of interlayer folding back position information isperformed, for example, upon session closing or when the disc 1 isejected while session closing is not performed.

[0245] First, a process of recording interlayer folding back positioninformation in a session closing process is described.

[0246]FIG. 15 illustrates a process executed by the controller 12 as asession closing process.

[0247] For example, when a session closing process is to be performed inresponse to an instruction from the host apparatus after user data arerecorded in such a manner as seen in FIG. 9A or when an instruction toclose a certain session is received from the host apparatus in suchmulti-session recording as illustrated in FIG. 10, the session closingprocess of FIG. 15 is executed. It is to be noted here that, in thefollowing description, interlayer folding back position information isrecorded into the byte positions D42 to D45 of an SDCB.

[0248] Referring to FIG. 15, if a session closing instruction (sessionclosing command) is issued from the host apparatus, then the controller12 discriminates at step F101 of FIG. 15 that session closing isnecessary, and then advances the processing to step F102.

[0249] At step F102, the controller 12 discriminates whether or not thesession of the object of the session closing instruction is recordedspanning recording layers.

[0250] If it is discriminated that the session is not recorded spanningrecording layers, then the controller 12 advances the processing to stepF104, at which the controller 12 writes all zero data into the bytepositions D42 to D45 of the SDCB shown in FIG. 11. In other words, thecontroller 12 writes an SDCB which includes all zero data into the bytepositions D42 to D45 thereby to update the SDCB.

[0251] On the other hand, if the controller 12 discriminates that thesession is recorded spanning recording layers, then the processingadvances to step F103, at which the controller 12 records the address ofthe actual folding back point, that is, interlayer folding back positioninformation, into the byte positions D42 to D45 of the SDCB of FIG. 11.In short, an SDCB having the value of the interlayer folding backposition information is written into the byte positions D42 to D45thereby to update the SDCB.

[0252] It is to be noted that, since the disc drive apparatus(controller 12) itself performs data writing on the disc 1, it graspswhether or not interlayer folding back is performed within the sessionwhich currently is in an open state and besides the address of thefolding back position in a case wherein the interlayer folding back isperformed. Therefore, the disc drive apparatus can carry out theprocesses at steps F102 to F104.

[0253] Thereafter, the processing advances to step F105, at which thecontroller 12 actually executes data writing as a session closingprocess.

[0254] It is to be noted that, in the single session recording, thewriting at steps F103 to F105 in the process, that is, recording of theinterlayer folding back position information and recording of thesession closing, are performed in the lead-in area and the lead-out areain such a manner, for example, as seen in FIG. 9B.

[0255] On the other hand, in order to close the first session in themulti-session recording, the writing at steps F103 to F105 is performedin the lead-in area and the closure of the session.

[0256] Further, in order to close the last session in the multi-sessionrecording, the writing at steps F103 to F105 is performed in the introof the session and the lead-out area.

[0257] Furthermore, in order to close an intermediate session in themulti-session recording, the writing at steps F103 to F105 is performedin the intro and the closure of the session.

[0258] In this manner, if, upon session closing, interlayer folding backis performed within the session, then the interlayer folding backposition information is recorded into the SDCB in the session thereby toeliminate the disadvantages described hereinabove with reference to FIG.10.

[0259] It is to be noted that, although it is discriminated at step F102whether or not the session spans recording layers, it is appropriate forthe processing to advance to step F103 also when the data recordingreaches the maximum recording range (last end of the data zone ofFIG. 1) in a session of the layer 0 in the multi-session recording. Inparticular, when a next session is recorded, the recording is performedfor the layer 1 without fail, and since the boundary of the sessionbecomes an interlayer folding back point, it is appropriate to recordthe position as an interlayer folding back position on the disc.

[0260] Further, although it is described above that the interlayerfolding back position information is recorded at the byte positions D42to D45 of the SDCB, also where the session item type 3 (layer item) inthe SDCB is used to record the interlayer folding back positioninformation, the process of FIG. 15 can be applied similarly.

[0261] 2-3. Process upon Ejection

[0262] Now, a process upon ejection is described with reference to FIG.16.

[0263] The process illustrated in FIG. 16 is executed, for example, whenthe user performs an ejection operation of the disc drive apparatus inorder to unload the disc 1 while no session closing instruction isissued from the host apparatus. In other words, the process is executedwhen the user tries to unload the disc 1 without performing a sessionclosing operation.

[0264] If a disc unloading request is detected at step F201, then theprocessing of the controller 12 advances to step F202.

[0265] The disc unloading request may be an eject command issued fromthe host apparatus to the disc drive apparatus or a depression operationby the user of an eject button provided on the disc drive apparatus.

[0266] When the processing advances to step F202 in response to a discunloading request, the controller 12 discriminates whether or not asession which is not closed as yet remains on the disc 1. If a sessionwhich is not closed as yet remains on the disc 1, then the controller 12discriminates whether or not recorded data span the recording layers.

[0267] If data are not recorded spanning the recording layers, then theprocessing advances to step F204, at which the controller 12 performsdisc unloading control. In other words, the disc 1 is unloaded while thedisc 1 is in a session open state.

[0268] On the other hand, if it is discriminated at step F202 that dataare recorded spanning the recording layers, then the processing advancesto step F203.

[0269] At step F203, the controller 12 updates only the SDCB in thesession without performing a session closing operation. In particular,the controller 12 records an SDCB in which an address of the actualfolding back point, that is, interlayer folding back positioninformation, is recorded at the byte positions D42 to D45 illustrated inFIG. 11 thereby to update the SDCB.

[0270] Then, the controller 12 performs the disc unloading process atstep F204, whereafter it ends the processing. In short, although thesession remains in an open state, the disc 1 is unloaded with theinterlayer folding back position information recorded thereon.

[0271] It is to be noted that, in single session recording or when anejection request is issued while the first session remains open inmulti-session recording, the writing executed at step F203, that is, theSDCB updating for recording of the interlayer folding back positioninformation, is performed in the identification zone in the lead-inarea.

[0272] Further, when an ejection request is issued while a certainsession from among the second and succeeding sessions remains open inmulti-session recording, the writing executed at step F203, that is, theSDCB updating for recording of the interlayer folding back positioninformation, is performed in the identification zone in the intro of thesession.

[0273] In the format in the DVD system of the recordable type, it isprescribed that, when a DCB (including an SDCB) is updated, another DCBfor replacement is recorded immediately next to a DCB recorded last.Further, it is prescribed that, if a plurality of DCBs having the samecontent descriptor exist, only that one of the DCBs which has thehighest address number is valid.

[0274] Accordingly, even with a write-once medium, there is no problemto update an SDCB within a region of the lead-in area or an intro beforesession closing.

[0275] In this manner, if, upon ejection, interlayer folding back isperformed within a session which is in an open state, then interlayerfolding back position information is recorded into the SDCB in thesession, and the disadvantages described hereinabove with reference toFIG. 9 are eliminated.

[0276] It is to be noted that, although it is discriminated at step F202whether or not a session which is not in a closed state spans therecording layers, further it is appropriate for the processing toadvance to step F203 also when the data recording of the session of thelayer 0 which is not in a closed state reaches the maximum recordingrange (last end of the data zone of FIG. 1) irrespective ofmulti-session recording or single session recording. In particular, whenadditional recoding to the session is performed or when the session isclosed and a next session is recorded, the recording is performed forthe layer 1 without fail, and since the boundary of the session becomesan interlayer folding back point, it is appropriate to record theposition as an interlayer folding back position on the disc.

[0277] Further, although it is described above that the interlayerfolding back position information is recorded at the byte positions D42to D45 of the SDCB, also where the session item 3 (layer item) in theSDCB is used to record the interlayer folding back position information,the process of FIG. 16 can be applied similarly.

[0278] 2-4. SDCB Updating Process upon Occurrence of Interlayer FoldingBack

[0279] Now, an SDCB updating process upon occurrence of interlayerfolding back is described with reference to FIG. 17.

[0280] The SDCB updating process is a process of recording, duringrecording operation, an SDCB including interlayer folding back positioninformation at a point of time at which advancement of the recordingpoint from the layer 0 to the layer 1 occurs.

[0281] It is to be noted that the following description is directed toan example wherein the session item type 3 of the SDCB is used to recordinterlayer folding back position information.

[0282] The controller 12 supervises, as a process relating to updatingof an SDCB, determination of a fragment end at step F301 of FIG. 17during data recording.

[0283] As described hereinabove, as a result of data recording in thedata zone, it is necessary to update the SDCB at a point of time whenrecording of one fragment is completed. Therefore, the discrimination atstep F301 is supervision of an SDCB updating timing at completion ofrecording of the fragment.

[0284] Then at step F302, occurrence of interlayer folding back issupervised. In other words, advancement of the recording operation fromthe layer 0 to the layer 1 is supervised. It is to be noted thatinterlayer folding back may possibly occur not only when the recordingoperation reaches the maximum recording range (last end of the data zoneof FIG. 1) of the layer 0 but also when the recording on the layer 0comes to an end before the maximum recording range is reached and therecording operation advances to the layer 1. In what conditioninterlayer folding back should be performed depends upon an applicationfrom which an instruction of operation of the disc drive apparatus isissued.

[0285] If it is discriminated at step F302 that interference foldingback occurs during recording operation, then the controller 12 advancesthe processing to step F303, at which the controller 12 updates the SDCBso as to add the session item type 3 (layer item). The layer item (referto FIG. 12C) includes an address as the interlayer folding back positioninformation.

[0286] The process described above is described below with reference toFIGS. 18 and 13(a) to 13(c).

[0287] It is assumed that fragments Frag#1 and Frag#2 are formed alreadyin a certain session as seen in FIG. 18 and a further fragment Frag#3 iscurrently recorded on the layer 0.

[0288] At a point of time prior to the recording of the fragment Frag#3,the SDCBs #1 and #2 illustrated in FIG. 13B are recorded already, andthe SDCB#2 is valid.

[0289] The discrimination of occurrence of interlayer folding back atstep F302 is made at a point of time, for example, when the datarecording of the fragment Frag#3 reaches the interlayer folding backpoint of FIG. 18 (and it is to be subsequently started to continuerecording on the layer 1). At this point of time, the recording of thefragment Frag#3 is not completed as yet.

[0290] Here, the processing of the controller 12 records an SDCBincluding the interlayer folding back position information at step F303.For example, an SDCB#3 of FIG. 13B is recorded.

[0291] The SDCB#3 is the latest valid SDCB which includes, as sessionitems, fragment items corresponding to the fragments Frag#1 and Frag#2and a layer item in which the interlayer folding back positioninformation is recorded.

[0292] It is to be noted that, at the point of time at which theprocessing of the controller 12 advances to step F302 or F303, therecording of the fragment is not completed as yet. Therefore, therecording of the fragment is further continued.

[0293] For example, if it is assumed that recording of the fragmentFrag#3 is performed also on the layer 1 and then is completed as seen inFIG. 18, then the processing of the controller 12 advances from stepF301 to step F304.

[0294] At step F304, it is discriminated whether or not the last end ofthe current fragment is the last end of the layer 0, and the processingof the controller 12 branches depending upon the discrimination.

[0295] If the fragment Frag#3 is being recorded in the example of FIG.18, then since the last end of the fragment Frag#3 is not the last endof the layer 0, the processing advances to step F306.

[0296] At step F306, the controller 12 performs updating of the SDCB inaccordance with an end of recording of a fragment. In particular, in theexample of FIG. 18, the controller 12 updates the SDCB so as to add acorresponding session item type 1 (fragment item) to the fragmentFrag#3. For example, the controller 12 writes an SDCB#4 of FIG. 13B.

[0297] In the example of FIGS. 18 and 13A to 13C, the SDCB#4 written atstep F306 becomes the latest valid SDCB in which fragment itemscorresponding to the fragments Frag#1, Frag#2 and Frag#3 and a layeritem in which the interlayer folding back position information isrecorded are included as session items.

[0298] It is to be noted that the case wherein the last end of afragment is discriminated as the last end of the layer 0 at step F304 isa case wherein additional recording to the session (recording of a nextfragment) is performed later or another case wherein the session isclosed and a next session is recorded, and in both cases, subsequentrecording is performed inevitably on the layer 1.

[0299] In short, in the present example, both of occurrence ofinterlayer folding back and completion of recording of a fragment aredetermined as SDCB updating timings as at steps F303 and F306 asdescribed above, and the case wherein the last end of a fragment becomesthe last end of the layer 0 is a case wherein an SDCB updating timing byoccurrence of interlayer folding back and an SDCB updating timing bycompletion of recording of a fragment become coincident witch other.

[0300] In this instance, the processing of the controller 12 advances tostep F305, at which the controller 12 performs updating of the SDCB. Inthis instance, however, the controller 12 updates the SDCB so as to adda session item type 1 (fragment item) corresponding to the currentfragment and a session item type 3 (layer item) in which the interlayerfolding back position information is recorded.

[0301] It is to be noted that, where the process of FIG. 17 is performedin single session recording or upon recording in the first session inmulti-session recording, the recording of an SDCB executed at stepsF303, F305 and F306 is performed for the identification zone in thelead-in area.

[0302] On the other hand, where the process of FIG. 17 is performed uponrecording in a certain session from among the second and followingsessions in multi-session recording, the recording of an SDCB executedat steps F303, F305 and F306 is performed for the identification zone inthe intro of the session.

[0303] In the example of the process of FIG. 17, when the recordingpoint from one to the other of the recording layers, the interlayerfolding back position information is recorded in the SDCB.

[0304] In short, the time lag between the occurrence of interlayerfolding back and the recording of the interlayer folding back positioninformation is shortest. That the time lag is shortest in this manner ismost safe for the assurance of the interlayer folding back position.This is because, even if interruption of power supply or the like occurswithin a period before later session closing or ejection is performed,the interlayer folding back position information is secured on the disc1.

[0305] It is to be noted that, since, in the process of FIG. 17, theSDCB is updated at a point of time when user data recording on the layer0 is completed and then user data recording on the layer 1 is started,interruption of the user data recording and accessing of the opticalpickup 3 are required additionally in the recording operation. If thesituation is such that the additional requirement is not preferable,then the process of FIG. 15 or 16 may be executed appropriately.

[0306] Incidentally, while the example of the process of FIG. 17 isdescribed in connection with an example wherein the session item type 3(layer item) in the SDCB is used to record interlayer folding backposition information, the example of the process of FIG. 17 can beadopted also where interlayer folding back position information isrecorded into the byte positions D42 to D45 of the SDCB.

[0307] 3. Modifications

[0308] While the preferred embodiment of the present invention isdescribed above, various modifications and applications are possiblewith the present invention.

[0309] While it is described above that interlayer folding back positioninformation is recorded at such specific timings as upon session closingprocessing, upon ejection and upon occurrence of interlayer foldingback, it may be performed at some other different timings.

[0310] For example, interlayer folding back position information may berecorded in response to a command from the host apparatus. As thecommand from the host computer, a command which designates a particularaddress as an interlayer folding back address may be issued before orduring user data recording. If the interlayer folding back address isspecified by such a command as just described, then recording ofinterlayer folding back position information (for example, such aprocess as at step F103, F203, F303 or F305 described hereinabove) maybe executed at a predetermined point of time. Naturally, where such acommand as described above is issued before or during user datarecording and interlayer folding back is performed in response to thecommand, such a process as described above with reference to FIG. 17 maybe performed to record the interlayer folding back position information.

[0311] However, it is otherwise possible to generate, as a command fromthe host computer, a command for directly instructing for recording ofinterlayer folding back position information. In short, not such acommand to “designate an interlayer folding back position” but a commandto “record interlayer folding back position information” is used. Thecontroller 12 may perform, in response to the command to “recordinterlayer folding back position information”, for example, theprocesses at steps F102 to F104 of FIG. 15 or the processes at stepsF202 to F203 of FIG. 16.

[0312] Also it is possible to record interlayer folding back positioninformation in response to an instruction regarding interlayer foldingback from the host apparatus as in the cases described above.

[0313] The processes illustrated in FIGS. 15, 16 and 17 and therecording process of interlayer folding back position information whichis performed in response to an instruction from the host apparatus asdescribed above can be applied similarly to both of a disc of theopposite track path and a disc of the parallel track path.

[0314] Further, while, in the foregoing description of the embodiment, aDVD+R is taken as an example of a two-layer recordable DVD type disc,also two-layer discs in the form of a DVD−R, a DVD+RW, a DVD−RW and aDVD-RAM can be suitably used similarly to record interlayer folding backposition information as described above.

[0315] Further, the region into which interlayer folding back positioninformation is to be recorded is not limited to the byte positions D42to D45 of the SDCB or the region of a session item, but may be set toany suitable position. In particular, the region may be set within theSDCB or may be some other region. Further, the interlayer folding backposition information is not limited to information of 4 bytes or 3bytes.

[0316] For example, the DVD-R/RW has a region called RMD (RecordingManagement Data), and interlayer folding back position information maybe recorded in such a region from Field13 to Fieldl4 of the RMD.

[0317] Further, it is effective to record interlayer folding backposition information not only on discs of the DVD type but also onvarious other recording media having a plurality of recording layerssuch as discs of other types such as discs of the CD type and discs ofthe blue ray disc type and various media other than disc media. In suchrecording media as mentioned above, the recording region may bedetermined suitably based on the data format used therefor.

[0318] Further, while, in the embodiment described above, the disc is atwo-layer disc, naturally the present invention can be applied suitablyalso to those recording media which have three or more recording layers.

[0319] While a preferred embodiment of the present invention has beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the followingclaims.

What is claimed is:
 1. A recording medium, comprising: a plurality of recording layers into which data can be written; each of said recording layers having a data area into and from which main data are to be recorded and reproduced, a preceding area which is to be formed at a position preceding to said data area, and an end area succeeding said data area; said recording medium having a region into which, in response to a fact that recording on a certain one of said recording layers reaches a maximum recording range or that data recording advances from a certain one of said recording layers to a next one of said recording layers, interlayer folding back position information indicative of a position to which the data recording advances is to be recorded.
 2. A recording medium according to claim 1, wherein the region into which the interlayer folding back position information is to be recoded is provided in the data area.
 3. A recording medium according to claim 1, wherein the region into which the interlayer folding back position information is to be recoded is provided in said preceding area or said end area.
 4. A recording apparatus for a recording medium which has a plurality of recording layers into which data can be written and each of which has a data area into and from which main data are to be recorded and reproduced, a preceding area which is to be formed at a position preceding to said data area, and an end area succeeding said data area, comprising: a recording block for recording information on any of the recording layers; and a control block for controlling, when, in a recording operation by said recording block, recording on a certain one of said recording layers reaches a maximum recording range or data recording advances from a certain one of said recording layers to a next one of said recording layers, said recording block to record interlayer folding back position information indicative of a position to which the data recording advances into a predetermined region on the recording medium.
 5. A recording apparatus according to claim 4, wherein, when a certain session formed on the recording medium by a recording operation of said recording block is to be closed, if advancement of the data recording from a certain one of the recording layers to a next one of the recording layers is performed within the session, then said control block controls said recording block to record the interlayer folding back position information.
 6. A recording apparatus according to claim 4, wherein, when the recording medium on which a recording operation has been performed by said recording medium is to be unloaded, if advancement of the data recording from a certain one of the recording layers to a next one of the recording layers is performed within a session on the recording medium which is not closed as yet, then said control block controls said recording block to record the interlayer folding back position information.
 7. A recording apparatus according to claim 4, wherein, when advancement of the data recording by a recording operation of said recording block from a certain one of the recording layers to a next one of the recording layers is performed, then said control block controls said recording block to record the interlayer folding back position information.
 8. A recording apparatus according to claim 4, wherein said control block controls said recording block to record the interlayer folding back position information in response to an instruction from an external host apparatus.
 9. A recording apparatus according to claim 4, wherein said control block controls said recording block to record the interlayer folding back position information into a predetermined region in the data area of the recording medium into which management information of a session is to be recorded.
 10. A recording apparatus according to claim 4, wherein said control block controls said recording block to record the interlayer folding back position information into a predetermined region in the preceding area or the end area of the recording medium into which management information of a session is to be recorded.
 11. A recording method for recording on a recording medium which has a plurality of recording layers into which data can be written and each of which has a data area into and from which main data are to be recorded and reproduced, a preceding area formed at a position preceding to said data area, and an end area succeeding said data area, comprising: a step of recording information on any of the recording layers; and a step of controlling, in response to a fact that recording on a certain one of the recording layers reaches a maximum recording range or data recording advances from a certain one of the recording layers to a next one of the recording layers at the recording step, so that interlayer folding back position information indicative of a position to which the data recording advances is recorded into a predetermined region on the recording medium.
 12. A recording method according to claim 11, wherein the control step is executed if, when a certain session formed on the recording medium by the recording step is to be closed, advancement of the data recording from a certain one of the recording layers to a next one of the recording layers is performed within the session.
 13. A recording method according to claim 11, wherein the control step is executed if, when the recording medium on which a recording operation has been performed by the recording step is to be unloaded, advancement of the data recording from a certain one of the recording layers to a next one of the recording layers is performed within a session on the recording medium which is not closed as yet.
 14. A recording method according to claim 11, wherein the control step is executed when advancement of the data recording by a recording operation at the recording step from a certain one of the recording layers to a next one of the recording layers is performed.
 15. A recording method according to claim 11, wherein the control step is executed in response to an instruction from an external host apparatus. 